
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>自动改变方向——幻灯片效果</title>
<style>
body,div,ul,li{margin:0;padding:0;}
ul{list-style-type:none;}
body{background:#000;text-align:center;font:12px/20px Arial;}
#box{position:relative;width:492px;height:172px;background:#fff;border-radius:5px;border:8px solid #fff;margin:10px auto;}
#box .list{position:relative;width:490px;height:170px;overflow:hidden;border:1px solid #ccc;}
#box .list li{position:absolute;top:0;left:0;width:490px;height:170px;opacity:0;filter:alpha(opacity=0);}
#box .list li.current{opacity:1;filter:alpha(opacity=100);}
#box .count{position:absolute;right:0;bottom:5px;}
#box .count li{color:#fff;float:left;width:20px;height:20px;cursor:pointer;margin-right:5px;overflow:hidden;background:#F90;opacity:0.7;filter:alpha(opacity=70);border-radius:20px;}
#box .count li.current{color:#fff;opacity:1;filter:alpha(opacity=100);font-weight:700;background:#f60;}
#tmp{width:100px;height:100px;background:red;position:absolute;}
</style>
<script type="text/javascript">
window.onload = function ()
{
	var oBox = document.getElementById("box");
	var aUl = document.getElementsByTagName("ul");
	var aImg = aUl[0].getElementsByTagName("li");
	var aNum = aUl[1].getElementsByTagName("li");
	var timer = play = null;
	var i = index = 0;	
	var bOrder = true;
	
	//切换按钮
	for (i = 0; i < aNum.length; i++)
	{
		aNum[i].index = i;
		aNum[i].onmouseover = function ()
		{
			show(this.index)
		}
	}
	
	//鼠标划过关闭定时器
	oBox.onmouseover = function ()
	{
		clearInterval(play)	
	};
	
	//鼠标离开启动自动播放
	oBox.onmouseout = function ()
	{
		autoPlay()
	};	
	
	//自动播放函数
	function autoPlay ()
	{
		play = setInterval(function () {
			//判断播放顺序
			bOrder ? index++ : index--;			
			
			//正序
			index >= aImg.length && (index = aImg.length - 2, bOrder = false);
			
			//倒序
			index <= 0 && (index = 0, bOrder = true);
			
			//调用函数
			show(index)
		},2000);	
	}
	autoPlay();//应用
	
	//图片切换, 淡入淡出效果
	function show (a)
	{
		index = a;
		var alpha = 0;
		for (i = 0; i < aNum.length; i++)aNum[i].className = "";
		aNum[index].className = "current";
		clearInterval(timer);			
		
		for (i = 0; i < aImg.length; i++)
		{
			aImg[i].style.opacity = 0;
			aImg[i].style.filter = "alpha(opacity=0)";	
		}
		
		timer = setInterval(function () {
			alpha += 2;
			alpha > 100 && (alpha =100);
			aImg[index].style.opacity = alpha / 100;
			aImg[index].style.filter = "alpha(opacity = " + alpha + ")";
			alpha == 100 && clearInterval(timer)
		},20);
	}
};
</script>
</head>
<body>
<div id="box">
    <ul class="list">
        <li class="current"><img src="img/01.jpg" width="490" height="170" /></li>
        <li><img src="img/02.jpg" width="490" height="170" /></li>
        <li><img src="img/03.jpg" width="490" height="170" /></li>
        <li><img src="img/04.jpg" width="490" height="170" /></li>
        <li><img src="img/05.jpg" width="490" height="170" /></li>
    </ul>
    <ul class="count">
        <li class="current">1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
    </ul>
</div>
</body>
</html>
